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		<span class="header-logo header-affix margin-left-no margin-right-no" data-offset-top="213" data-spy="affix">[Usaco2007 Nov]Cow Hurdles 奶牛跨栏</span>
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                [Usaco2007 Nov]Cow Hurdles 奶牛跨栏                </h1>
                <p>时间限制：5s&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;  空间限制：64MB</p>			</div>
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                                <h3>题目描述</h3><p><p><span style="font-size: medium">Farmer John 想让她的奶牛准备郡级跳跃比赛，贝茜和她的伙伴们正在练习跨栏。她们很累，所以她们想消耗最少的能量来跨栏。 显然，对于一头奶牛跳过几个矮栏是很容易的，但是高栏却很难。于是，奶牛们总是关心路径上最高的栏的高度。 奶牛的训练场中有 N (1 &le; N &le; 300) 个站台，分别标记为1..N。所有站台之间有M (1 &le; M &le; 25,000)条单向路径，第i条路经是从站台Si开始，到站台Ei，其中最高的栏的高度为Hi (1 &le; Hi &le; 1,000,000)。无论如何跑，奶牛们都要跨栏。 奶牛们有 T (1 &le; T &le; 40,000) 个训练任务要完成。第 i 个任务包含两个数字 Ai 和 Bi (1 &le; Ai &le; N; 1 &le; Bi &le; N)，表示奶牛必须从站台Ai跑到站台Bi，可以路过别的站台。奶牛们想找一条路径从站台Ai到站台Bi，使路径上最高的栏的高度最小。 你的任务就是写一个程序，计算出路径上最高的栏的高度的最小值。 </span></p></p><hr/><h3>输入格式</h3><p><p><span style="font-size: medium">行 1: 两个整数 N, M, T 行 </span></p>
<p><span style="font-size: medium">2..M+1: 行 i+1 包含三个整数 Si , Ei , Hi 行 M+2..M+T+1: 行 i+M+1 包含两个整数，表示任务i的起始站台和目标站台: Ai , Bi</span></p></p><hr/><h3>输出格式</h3><p><p><span style="font-size: medium">行 1..T: 行 i 为一个整数，表示任务i路径上最高的栏的高度的最小值。如果无法到达，输出 -1。 </span></p></p><hr/><h3>样例输入</h3><pre>5 6 3
1 2 12
3 2 8
1 3 5
2 5 3
3 4 4
2 4 8
3 4
1 2
5 1
</pre><hr/><h3>样例输出</h3><pre>4
8
-1
</pre><hr/><h3>提示</h3><p>没有写明提示</p><hr/><h3>题目来源</h3><p>Silver</p>
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